[GitHub] [helix] Marcosrico commented on a diff in pull request #2327: Meta client - implement CRUD for zkMetaClient

[GitBox <gi...@apache.org>]

Marcosrico commented on code in PR #2327:
URL: https://github.com/apache/helix/pull/2327#discussion_r1063002783


##########
meta-client/src/main/java/org/apache/helix/metaclient/impl/zk/ZkMetaClient.java:
##########
@@ -49,55 +61,97 @@ public ZkMetaClient(ZkMetaClientConfig config) {
   }
 
   @Override
-  public void create(String key, Object data) {
-
+  public void create(String key, T data) {
+    // TODO: This function is implemented only for test. It does not have proper error handling
+    _zkClient.create(key, data, ZooDefs.Ids.OPEN_ACL_UNSAFE, CreateMode.PERSISTENT);
   }
 
   @Override
-  public void create(String key, Object data, EntryMode mode) {
+  public void create(String key, T data, EntryMode mode) {
 
   }
 
   @Override
-  public void set(String key, Object data, int version) {
-
+  public void set(String key, T data, int version) {
+    try {
+      _zkClient.writeData(key, data, version);
+    } catch (ZkException e) {
+      throw translateZkExceptionToMetaclientException(e);
+    }
   }
 
   @Override
-  public Object update(String key, DataUpdater updater) {
-    return null;
+  public T update( String key, DataUpdater<T> updater) {
+    org.apache.zookeeper.data.Stat stat = new org.apache.zookeeper.data.Stat();
+    // TODO: add retry logic for ZkBadVersionException.
+    try {
+      T oldData = _zkClient.readData(key, stat);
+      T newData = updater.update(oldData);
+      set(key, newData, stat.getVersion());
+      return newData;
+    } catch (ZkException e) {
+      throw translateZkExceptionToMetaclientException(e);
+    }
   }
 
   @Override
   public Stat exists(String key) {
-    return null;
+    org.apache.zookeeper.data.Stat zkStats;
+    try {
+      zkStats = _zkClient.getStat(key);
+      if (zkStats == null) {
+        return null;
+      }
+      return new Stat(EphemeralType.get(zkStats.getEphemeralOwner()) == EphemeralType.VOID
+          ? EntryMode.PERSISTENT : EntryMode.EPHEMERAL, zkStats.getVersion());
+    } catch (ZkException e) {
+      throw translateZkExceptionToMetaclientException(e);
+    }
   }
 
   @Override
-  public Object get(String key) {
-    return null;
+  public T get(String key) {
+    return _zkClient.readData(key, true);
   }
 
   @Override
-  public List<String> getDirestChildrenKeys(String key) {
+  public List<OpResult> transactionOP(Iterable<Op> ops) {
     return null;
   }
 
   @Override
-  public int countDirestChildren(String key) {
-    return 0;
+  public List<String> getDirectChildrenKeys(String key) {
+    try {
+      return _zkClient.getChildren(key);
+    } catch (ZkException e) {
+      throw new MetaClientException(e);
+    }
+  }
+
+  @Override
+  public int countDirectChildren(String key) {
+    return _zkClient.countChildren(key);
   }
 
   @Override
   public boolean delete(String key) {
-    return false;
+    try {
+      return _zkClient.delete(key);
+    } catch (ZkException e) {
+      throw new MetaClientException(e);

Review Comment:
   Given that the `MetaClientException` is caught in the `translateZkExceptionToMetaclientException` method, what is the reason for not using the latter all the time? I assume readability is better if the exception is known to be a general one but perhaps then we would want to remain consistent with the other errors and catch/throw each individual type. Just a thought



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